Our overall goal for this proposal is to examine the effects of U.S. state parity laws and Medicaid expansion programs implemented in various states between 2004 through 2013 on treatment of substance use disorders (SUD), unmet need for such treatments and variation in the mix and length of treatments. The Patient Protection and Affordable Care Act (PPACA) of 2010 (fully implemented in 2014) and the Mental Health Parity and Addiction Equity Act (MHPAEA) of 2008 are expected to change the SUD treatment system drastically. Although these regulations are yet to be fully implemented, variations in the content of behavioral health services under PPACA and the Federal Court decision allowing states to opt out of the Medicaid expansion clause of the PPACA will likely result in significant variations in coverage across states. In years prior, a number of states implemented programs to extend behavioral health parity in the private insurance market. Some states also enacted Medicaid expansion programs. The impact of these programs on the use of SUD treatment services, mix of services, and outcome of treatments has not been fully examined. Assessment of these earlier state-level programs can help policy makers predict the future effects of PPACA and MHPAEA and their state-level variations, to characterize expected changes in demand for services or changes in treatment settings, and to identify groups of individuals who would least benefit from these policies. Towards these aims, our current project proposes to use data from over 450,000 US adults who participated in the annual National Survey of Drug Use and Health between 2004 and 2013, as well as national administrative data from the Treatment Episode Data Sets (TEDS) comprised of information from millions of admissions and discharges to SUD treatment facilities in this same period to examine the impact of state parity and Medicaid expansion programs on patterns of SUD treatments. We also aim to examine whether these health reforms impacted specific subgroups of the population differentially and to assess the effectiveness of services among individuals who received treatment as a result of these state reforms. Our assessment of these earlier state reforms would potentially provide information that is directly applicable to the design and implementation of the future systems of care for substance use disorders.